Purpose: This study aimed to develop and validate a scale for measuring what influences students' academic achievement in the Badminton 1 course at Saigon University, Vietnam. While physical education research often discusses skill acquisition broadly, no instrument has been designed specifically for badminton instruction in Vietnamese universities. 

Methods: This study employed a mixed-methods design across two phases. In the qualitative phase, semi-structured interviews with 30 experts (physical education lecturers and administrators) were conducted to develop a preliminary scale. In the quantitative phase, a survey was administered to 1,846 undergraduate students who had completed the Badminton 1 course during the 2024-2025 academic year. Data were analyzed using Cronbach's Alpha for reliability assessment, Exploratory Factor Analysis (EFA) for construct validity, and Multiple Linear Regression to determine the relative influence of factors on academic achievement. The dependent variable—academic achievement—was measured using seven items with a Cronbach's Alpha of 0.941. 

Results: The final scale comprised seven factors with 34 observed variables. Cronbach's Alpha coefficients for all factors ranged from 0.942 to 0.993, indicating excellent internal consistency. The EFA results confirmed the seven-factor structure, which cumulatively explained 93.38% of the variance in the observed variables, with the Kaiser-Meyer-Olkin (KMO) measure of 0.892 and Bartlett's test of sphericity significant (χ² = 119,330.515, p < 0.001). The multiple linear regression model was significant (F = 217.226, p < 0.001), with an Adjusted R² of 0.451, indicating that the seven factors explained 45.1% of the variance in academic achievement. The order of influence, determined by standardized beta coefficients, was: (1) Teaching Methods (β = 0.336), (2) Assessment Methods (β = 0.319), (3) Lecturer Competence (β = 0.292), (4) Course Curriculum (β = 0.272), (5) Facilities (β = 0.237), (6) Learning Attitude (β = 0.234), and (7) Learning Methods (β = 0.212).